The Light Against the Dark
by Grac3
Summary: Part nine of the Loki and the Doctor series. After a lovely picnic on Asgard with his wife, the Doctor intends to take River to see an old friend of his. Unfortunately, he isn't in his cell where he's supposed to be. Twoshot. Episode tag: Dark World / Post-The Angels Take Manhattan
1. Tonight

**Warning:** Blood and gore

 **Spoilers for: The Time of the Doctor**

 **Disclaimer: Don't own Thor or Doctor Who**

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Chapter 1 – Tonight

"That was wonderful, sweetie."

River leaned over to give the Doctor a peck on the lips.

She sat back and pulled a compact mirror from her pocket.

"I'm glad. But there's still one more thing I have planned to show you."

River snapped the mirror shut and turned to face the Doctor. "More?"

The Doctor nodded.

River grinned. "Sounds exciting. Where are we going?"

The Doctor said nothing, but his eyes were filled with mischief. "You'll see."

The Doctor pulled their picnic basket round so that they could pack everything away and politely pretended to be completely focused on the plates he was stacking while River gorged herself on the last few strawberries.

Once everything had been put away, the Doctor stood and pulled River up beside him. She rested her hand in the crook of the Doctor's elbow, and he begun on the way down from the green hills and into the city.

The town was immensely busy, with people bustling around wherever they looked. River's eye would occasionally catch something and she would send an enquiring look the Doctor's way, but he merely smirked and continued on. When it became more obvious that they were headed towards the huge golden citadel in the centre of the city, River spoke up.

"Doctor…"

The Doctor kept his face turned from her, and his gaze fixed on the structure before them.

It only took a few flashes of the psychic paper to get them into the palace and down to the lower levels.

With each staircase they descended, River's suspicion grew.

"Where are we going?"

The Doctor gave her a small smile. "To see an old friend."

A few moments later, they reached the lowest level of the citadel. They emerged at the end of a wide corridor lit by artificial light with cells on either side: large rooms cut off from the rest by grids of crackling golden light. Some had several prisoners inside, others only one. All of the poor incarcerated looked considerably worse for wear; some were even sporting black eyes or other minor injuries.

Each had a guard stationed outside.

Each except one.

Halfway into the dungeons was an empty cell guarded by a woman in full armour. As soon as she saw River and the Doctor approach the cell she was guarding, she drew her sword and assumed a defensive position.

"Who are you?"

"I'm the Doctor, and this is River Song. And you must be Sif! Wasn't expecting to see you here, today. What a surprise!" The Doctor grinned.

The woman's eyes narrowed and the blade inched a little further to the Doctor's torso. "How do you know my name?"

The Doctor waved his hand. "That doesn't really matter right now. What matters, is where he?" He pointed to the cell.

Sif grit her teeth. "I don't see why that's any of your business."

The Doctor's eyes darkened.

"It's my business because I know that that man is a dangerous criminal, and you will need all the help you can get to find him before he does any damage. And I've met him outside of Asgard, so you could say I know a little more about his cosmic hiding places than you do."

Sif straightened, though she kept her sword pointed at the Doctor. "You know the Silvertongue."

The Doctor smiled sadly. "I'm sure he would be thrilled to hear you call him that."

Sif sneered. "I don't care if he's thrilled or repulsed; I'll call him what I like after what he's done."

"So you think he's alive?"

Sif snorted. "You think he's not?"

The Doctor shrugged. "How can I think anything either way when I don't know where he is? I was under the impression that he would be in this cell. That is why we're here, after all."

He gestured to himself and River.

"If you didn't know that he isn't here, then why should I enlighten you as to his whereabouts?"

"So you do know his whereabouts?"

"And you don't. Therefore, I believe, I have the upper hand."

The Doctor took a moment to reassess his strategy. He looked down at Sif's sword, still pointed at his chest. Quickly forming an idea, he straightened himself to his full height and assumed his most military pose.

"Lady Sif, you may have heard of me: I am the Oncoming Storm, the Predator of the Daleks, the Great Exterminator. I have fought long and hard to make this universe a safe place for all to live in, and we both know that Loki threatens that. Let me help you put an end to his dangerous exploits."

Sif stared at him, her eyes narrowed. "The Oncoming Storm? I have never heard of such a warrior. I pray, continue on your way. This is getting tiresome, and I would hate to actually have to run you through."

The Doctor sighed and turned to River.

"Darling, do you have your Vortex Manipulator?"

River smirked, already reaching for the black strap around her wrist. "Well ahead of you, sweetie."

There was a flash of blue light, though River was still by the Doctor's side when it faded.

Before them, Sif groaned and raised her free hand to her head.

"You…" she breathed, staring up at River with something like childlike wonder in her eyes. "You were… when I was a child… But… that never happened… But it did…"

Sif gasped; her eyes widened. "But… that means… I…" She turned to the Doctor with fear in her eyes. "Thor took Loki to Svartalfheim to give the Aether back to Malekith. They are yet to return."

The Doctor nodded. "Thank you."

~{Loki-and-the-Doctor}~

"So… Norse god of mischief and lies. You know me so well."

River leaned against the Doctor's back, resting her chin on her shoulder and trailing her hands down his arms while he fiddled with the TARDIS controls.

"Well, that was the idea," he mumbled.

"What's wrong?" River frowned. She stepped back. The Doctor moved around the control panel, flicking switches and pressing buttons. "Doctor?"

"Something doesn't feel right. He should have been in his cell. There must be something going on, especially if Thor is talking to Loki after what he did."

"What did he do?"

The Doctor waved it away. "It was a whole… New York thing."

River bit her lip. "Oh."

The Doctor leaned against the console and looked up at River. "Different New York thing."

"Obviously."

The Doctor pushed himself up from the panel. "Let's just say we have a shared hatred of that particular city. Shame, really. I had such a good time in the New New one…"

He trailed off and continued with his in-flight checks.

River regarded her husband. "You're worried."

"Well, he is the god of mischief and lies. Who knows what sort of trouble he's got himself into this time?"

River smirked. "Sounds like it'll be an adventure. And no offence, sweetie, but that's just what that picnic, lovely as it was, was lacking."

The Doctor said nothing as the TARDIS landed. He strode over to the door and wrenched it open. River sighed and followed him, stepping out after him into the bleak world beyond.

There was no life to be seen on this dark world: only dim light, black sand, and large rocks. The terrain made it tricky underfoot; while the Doctor strode onward with nary a worry, River was finding it so difficult to keep up in her heels. It didn't take long for the Doctor to be halfway across the dark landscape, while River was still only just out of the TARDIS.

"Loki!" the Doctor cried into the distance; he received no answer but the blowing of the wind. Dust was flying through the air and making it difficult to see ahead. "Thor!"

River was beginning to worry, as the Doctor showed no sign of stopping.

"Where is he? Where-"

River was too far behind the Doctor to see what had suddenly made him stop, but he was only stationary for a moment before he broke into a sprint. River did the same, as best she could. As she cleared a small crest, she noticed a green-clad figure lying on the ground. It wasn't moving.

"Doctor…"

The Doctor wasn't listening. He stopped next to the body and looked down at it, his hands curling into his hair.

He didn't move until River reached him. Then, he bent down, and – with hands shaking – reached two fingers forward to press into the figure's throat. His face fell.

"Doctor?"

The Doctor sat back on his haunches. "He's dead. Run through." He gestured to the red stain on Loki's middle.

River stood a few feet back from the Doctor, unable to see his face. He didn't move, and she didn't dare move closer.

A moment passed in which time didn't seem to have moved at all. Then, suddenly, he slammed his fist into the ground next to the body.

"No!"

River winced. "Doctor…"

"No, no, no, _no_!" He kept punching the ground until River was sure that he would break his skin – or his bones. "I still owe you! You can't die before I pay you back! I can't lose you as well! You are _not done_ in this universe."

The Doctor reached forward and grabbed Loki's shoulders. He shook the body, and blood seeped from the wound in his abdomen, dripping down onto the ground below. The Doctor watched with both revulsion and fascination as it pooled next to Loki's form. His gaze drifted back up to the fatal wound…

River saw something click in the Doctor's brain. He stood abruptly, twisted on his heel, and made for the TARDIS.

"Doctor?" River called after him as he passing by her without a second thought, but once again she was ignored. She huffed, checking that the Vortex Manipulator was still on her wrist before going to stand next to Loki's body.

She looked down at his face, so pale and peaceful in death, his hair tucked neatly under his head like someone had been there to arrange it before him.

River decided in that moment that if she ever met Thor, she would make him pay for whatever part he had played in the demise of this man – this friend of her husband.

She was brought from her thoughts by the sound of shoes scuffing on the dust underfoot. The Doctor was making his way back over with a jar in his hand: a jar filled with what looked suspiciously like nanogenes.

"Doctor, what are you doing?"

The Doctor still ignored her, walking over to Loki and kneeling by his side.

"Do nanogenes know the biology of demigods?"

"These ones do," the Doctor explained as he twisted the jar lid open and encouraged the nanogenes towards Loki's wound. "We once had a run-in with a sword-wielding Weeping Angel, and I healed him with these. I've been hanging on to them ever since; knew they'd come in handy one day."

River watched, fascinated, as the nanogenes got to work. The glowing lights swarmed around the wound, making it impossible to see what they were doing to the trickster's flesh. When they were done, they formed themselves into an almost perfect sphere and floated up from Loki's abdomen. The Doctor coaxed them back into the jar and placed the lid back on.

For a moment, it seemed as though they were too late: the wound was indeed fixed, for the flesh was visible and unmarred through the tear in his clothes, yet Loki still lay there, motionless and pale.

The Doctor stared down at his face.

Suddenly, Loki took in a deep breath, and his eyes flew open.


	2. Never Let Me Down

**Spoilers for: The Time of the Doctor**

 **Disclaimer: Don't own Thor or Doctor Who**

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Chapter 2 – Never Let Me Down

Loki sucked in a deep breath, fighting the urge to cough as his lungs filled with Svartalfheim dust. His hands reached for his abdomen, feeling for a wound – but found nothing. His clothes were still torn and sticky with blood, but there was no evidence of the mortal wound.

"I knew there was a reason I kept those things. You never know when you need to bring a friend back from the brink of death."

"Not the brink," Loki growled. He looked up and saw the face – well, one of the faces – he had been expecting to see. "You should know, being a Doctor and all."

"I thought I told you my doctorate was only honorary?"

The Doctor placed a hand on his shoulder as he pushed himself into a sitting position. The movement made his head swim; he raised a hand to his temple.

"Doctor, what have you done?"

Loki froze. Lowering his hand to his lap, he looked up and saw that there was someone else there, standing just behind the Doctor: a tall woman with wild hair and a terrified but angry expression on her face.

The Doctor turned to her. "I brought him back."

She shook her head slightly and looked for all the world like she wanted to back away from the scene before her.

"Time can't be rewritten. You know that better than anyone."

"This isn't rewriting time. I can sense when something is fixed, and not only is this not, but it was never supposed to happen in the first place."

The woman raised her brow at the Doctor. "And you're sure about that, are you?"

The Doctor looked back at Loki. "Positive."

Loki sneered and pushed himself to his feet. The Doctor stood as well.

"Well, as soon as the two of you stop gawping at me, I think I'll…"

He trailed off, coming to a sudden realisation.

He had nowhere to go.

If he went back to Asgard, he would just be sent straight back to his cell. He could go somewhere else, but he couldn't stand the thought of the possibility of getting stuck in the Void again. He wouldn't always have the Doctor around to pull him from that particular fate.

Loki turned to the Doctor. "Why did you save me?"

The Doctor's eyes darkened. "I owe you," he answered simply. "Why are you here?"

"The Aether was released. Jane Foster found it, and Malekith was after her. She had to be brought to safety, so Thor and I came here to get Malekith to release the Aether from her so that we could destroy it." Loki winced. "We failed."

"And you were killed."

Loki glared at the Doctor. He turned to the woman instead. "And who might you be?"

The woman took a moment to look affronted, but then extended her hand to Loki. "Professor River Song."

Loki took it, bringing it a little closer before he caught a glare directed at him from the Doctor, and he thought better of it.

"I know who you are," River interrupted as she brought her hand back, interrupting Loki as he opened his mouth to introduce himself. "I was hoping on meeting you today, though I was hoping you'd be a little less… undead."

The Doctor sighed. "He's not undead. This is why you shouldn't study archaeology. You don't get taught about nanogenes studying archaeology."

"Well, you didn't even pass your exams at the academy. Not the first time, anyway."

The Doctor rolled his eyes.

"I should never have let you read my two hundred year diary."

He turned back to Loki. "The question is, why were you helping Thor at all? I was under the impression that the two of you didn't get along anymore."

Loki was afraid that the Doctor would try to pull at that particular thread. He must have known what had happened; it had been a previous version of himself the last time, at least. He shot the Doctor a pointed look, and hoped that the Time Lord would understand.

The Doctor's eyes darkened. "Frigga."

Loki looked away sharply, forcing the memory of the guard's words from his brain. When he was slightly more composed, he rounded on the Doctor.

"You said you owe me."

The Doctor nodded. "Indeed I do. I still do."

Loki chuckled. "Is bringing me back from the dead not enough?"

"I fear not."

Loki snorted. "I hardly believe that. Though if you're still looking for ways to repay me, I would appreciate transportation from this godforsaken realm."

The Doctor gave Loki a sad smile. "Oh, I can do more than that."

The Doctor walked back off towards the TARDIS, with River and Loki following obediently behind. The Doctor ignored all of Loki's attempts to find out what he was planning, instead giving him a wry smile and continuing on his way.

The journey within the time ship was as disastrous and dangerous as Loki had always remembered. The ship shook violently, and even his strongest grip on the rails was not enough to keep him upright the entire time.

As they landed and he picked himself up off of the floor, he glared at River, who had, annoyingly, managed to remain completely balanced since they had taken off.

The Doctor pulled the last lever with a final flourish and ran for the door. As Loki and River tried to follow him, he held his hand up at them.

"I just have some quick business to attend to. I'll be back before you know it."

River scoffed, crossing her hands over her chest. "You know, I don't like being told what to do."

"No one worth their salt ever does." The Doctor smiled as he closed the door behind him.

Loki grit his teeth, staring at the closed door of the TARDIS. His hands balling into fists at his sides, he made to follow. He was stopped when a hand reached out to his chest.

"Not a good idea. The man may act like an idiot most of the time, but there are occasions when he knows what he's doing. He'll be back. This is his home, after all." River lowered her hand and stared wistfully up at the ceiling of the control room. "The only other woman he loves more than me."

An almost smug hum filled the room, and River's lip curled.

Loki turned to her fully, taking her in properly for the first time. She was certainly confident, and held herself in a certain way that spelled nothing but danger. Even so, something didn't quite add up…

"I thought the Doctor loved another."

River rounded on Loki, raising her brow. "Not at the moment. I am not so naïve to think I am the first, but I am the current, and that is enough for me. When you live as long as the Doctor, you get to know quite a few people."

"How old is he now?"

"He claims to be just over 1100. I doubt it, though. When I look in his eyes… I see so much more time. Far too much time."

"But he'll just keep changing and living on."

River shook her head. "Not now. This is his last face. He told me a while ago. He still has some regeneration energy, or at least he did. Not enough to completely change again, and he probably has nothing now." River lifted her hand, bending her wrist back and forth a couple of times. "The stupid fool."

Suddenly, the door to the TARDIS opened loudly, banging against the wall before being slammed shut again. The Doctor ran over to the console and began to flick the controls again. Loki made his way over to the railing to hold on for dear life.

It wasn't too long before the ship landed again. The Doctor was more solemn by this point; he stared at the ground, letting out a small sigh before he straightened himself up from where he was leaning against the control panel.

He gestured for Loki to leave first.

The trickster obeyed, curiosity getting the better of his frustration. He opened the door carefully and stepped out.

He faltered.

They were on a high ledge over a waterfall. At the banks, some hundreds of feet from where they stood, a boat was being pushed out.

Loki's knees felt weak, and if it weren't for the Doctor's hand dropping onto his shoulder a moment later, he felt that he would have fallen.

"Is that…" Loki breathed, staring at the boat as it neared where they were standing.

"Yes."

Loki gulped down the painful lump in his throat, though he couldn't stop the tears from falling. A flaming arrow soared through the sky and ignited the boat as it continued on its way towards the waterfall. It was followed by hundreds more: the other casualties of Asgard's brief but devastating battle with Malekith.

Loki only had eyes for one.

It floated off of the edge of the waterfall, though gravity soon took hold and pulled the boat down; its contents exploded into an uncountable number of glorious shining lights which drifted up into the dark sky.

On the banks, people began letting go of glowing spheres.

The Doctor patted Loki on the shoulder, but he couldn't look away from the scene before him.

"Loki," the Doctor said softly.

Reluctantly, Loki turned his head. The Doctor was holding a ball out to him.

"Go ahead," the Doctor told him softly.

With a grateful nod, Loki took the ball from the Doctor and lifted it to his lips, pressing a gentle kiss against it before releasing it into the sky. It floated up and out of sight.

When it was all over, the Doctor steered Loki gently back to the TARDIS, and took off once more.

Once the ship had landed, a moment passed in silence before Loki spoke.

"Where are we?"

The Doctor looked up from the control panel. "Exactly where we were before, the day that River and I were having our picnic on Asgard." He rolled up his sleeve and checked the watch on his wrist. "We should be heading to the palace to find you're not in your cell right now."

Loki's brow furrowed. "You are returning me to Asgard? For what purpose?"

"You don't have to stay here. I know you know other ways than the TARDIS to get to other worlds if you want. But right now, out there, they all think you're dead. Or at least, they will do pretty soon, if you want them to."

Loki's breath quickened. He tilted his head slightly and took a half-step away from the Doctor. "What are you saying?"

The Doctor sighed and ran a hand over his face. Suddenly Loki could see all of the years that were under the Doctor's belt: he looked so old – too old.

The Time Lord walked around the control panel and placed his hands on Loki's shoulders, looking him straight in the eyes.

"Loki, this is the last time you'll see me. I had wished that it would have been under better circumstances, but I hope that you can forgive me for all I've done to you. I won't have another face after this. This is my last life. I'm truly glad to have known you. But I want… no, I _need_ you to do something for me."

The Doctor licked his lips and tightened his grip on Loki's shoulders.

He smiled, though it didn't reach his eyes.

"I want you to start over. Make your life what you want it to be. Don't run into Thanos again. Be the boy I saw all that time ago in the library in the palace. Please, will you do this for me?"

Loki could barely remember what it had been like to be that person, who had only wanted to escape from training by hiding out in the library. It seemed like such a trivial problem now, compared to all that he had had to deal with since…

Yet staring at the Doctor's eyes now, and seeing the pain and age within them, he couldn't help but think that all the problems he'd had since then were just as trivial.

But what would he do without them?

"I will," he told the Doctor, and for a second, he almost saw the Time Lord's smile reach his eyes.

"Excellent."

The Doctor pulled Loki into a hug. "I'm so proud of you. I hope you're happy, in the end."

Loki found himself returning the embrace with fervour. Over the Doctor's shoulder, he saw River give him a wink.

"I hope so too."

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 **A.N.:** There is only one more story in the series after this! It's been a long time coming, so I hope you enjoy it.

 **UPDATE 13/06/2016:** The last part of the Loki and the Doctor series, The Flaw in the Calculations, has been posted.


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